1. Field of the Invention
Milk produced on dairy farms is generally collected by milk trucks every day or every other day. As milk is produced, it is fed from the milking parlour into a milk tank in which it is temporarily stored until it is collected by the milk truck. Such milk tanks are usually cleaned each time after the stored milk has been collected by the milk truck. The invention relates to a method of cleaning such a milk tank and to an apparatus for carrying out that method.
2. Description of the Prior Art
From French patent application 2 446 686 a method of cleaning a milk tank is known which includes a rinsing stage and a washing stage. The rinsing stage includes the steps of accumulating at least one predetermined first quantity of water from a water supply source in a buffer reservoir and subsequently rinsing the milk tank with the accumulated water. The washing stage comprising the steps of accumulating a predetermined second quantity of water from the water supply source, adding a cleaning agent to the water to form a cleaning solution and washing the milk tank with the cleaning solution.
More specifically, the water to be supplied to the milk tank during the washing stage is also dosed by accumulating the predetermined quantity of water in the buffer tank. To fill the buffer tank, valves in water supply conduits leading to the buffer tank are maintained in an opened condition for a time sufficient for filling the buffer reservoir with the required quantity of water if the lowest expected pressure in the water supply prevails. The actual quantity of water accumulated in the buffer tank is controlled by floater operated valves. These valves are closed when the water in the buffer tank reaches a predetermined level.
One problem of this known method is the long duration of the cleaning program. It is generally desirable to reduce the duration of the cleaning program to a minimum, so the feeding of milk to the milk storage tank can be resumed as soon as possible after the milk therein has been transferred into the milk truck.
Another problem is that a large buffer reservoir is required to contain all the washing water (generally 25 to 45 liters). The large buffer tank also complicates installing the cleaning apparatus.
This known method also leaves room for improvement with respect to the reliability of the water-dosing. If the water supply pressure is below the expected minimum or if a valve in the water supply is defective, the cleaning program will be carried out without any water or with too little water. Also, problems at the discharge side of the buffer tank, for example choking-up of the discharge aperture causing incomplete emptying of the buffer tank, are not detected and will also cause the cleaning program to be carried out with too little water. This can lead to incomplete removal of milk residues or cleaning agents. Insufficient cleaning of the tank and cleaning agents left behind in the tank after cleaning can have such a detrimental effect upon the milk stored in the tank, that a next tankload of milk may have to be rejected.
Yet another disadvantage of this known method is that the amounts of rinsing and washing water cannot be set independently of each other.